Care for Japanese Zelkova Bonsai

Japanese zelkova may be cultivated indoors on a sunny windowsill.

Japanese zelkova (Zelkova serrata) is a deciduous tree native to Japan, eastern China and Taiwan that is often enjoyed as a bonsai thanks to its pale gray bark long green leaves and resistance to common bonsai pests and diseases, including Dutch elm disease.

Location

Japanese zelkova may be grown outdoors in U.S. Department of Agriculture plant hardiness zones 5 to 8, where it will grow in full or partial sun. In the summer, the plant requires some protection from the sun, lest its leaves dry out. Move the tree or set up a temporary shade cover. Indoor plants need a sunny windowsill. If kept indoors, Japanese zelkova will keep its tender green leaves year-round. Indoor plants should be brought outdoors in late spring until fall to soak up a little extra sun. If you want the tree to drop its leaves for winter, keep the bonsai outside until they drop.

Soil

A sandy, loamy soil potting mix works best. The soil can be enhanced with a balanced liquid fertilizer, applied once a week in spring and summer. If the tree is allowed to stay evergreen in the winter, apply fertilizer once a month in the winter. Do not fertilize if the plant's leaves have dropped. If the roots of a young tree poke up out of the soil, cover them lightly with soil to help them develop more. Mature tree roots can be left showing above the soil, if you wish.

Moisture

Like other bonsais, Japanese zelkova must be watered frequently to ensure the soil never becomes completely dry. This may be up to twice a day during the summer. Water thoroughly so water drains out the hole in the bottom of the container. Do not water so often the soil is consistently wet, as this will lead to root rot. Reduce watering in the winter, about once every other day is usually adequate.

Maintenance

Young plants grow quickly and must be repotted annually in spring to keep their roots from growing out of control. Carefully remove the tree from the pot, brushing off excess dirt from the roots, and trim away the bottom one-fourth of the roots. Repot, using fresh soil, and water deeply. Pinching back new growth and pruning with a pair of sharp, concave scissors is usually enough to maintain a pleasing shape. Shaping with wire is tricky for novices and can permanently injure the tree if done incorrectly.

About the Author

Michelle Wishhart is a writer based in Portland, Ore. She has been writing professionally since 2005, starting with her position as a staff arts writer for City on a Hill Press, an alternative weekly newspaper in Santa Cruz, Calif. An avid gardener, Wishhart worked as a Wholesale Nursery Grower at Encinal Nursery for two years. Wishhart holds a Bachelor of Arts in fine arts and English literature from the University of California, Santa Cruz.